1. Field of the Invention
The present invention relates to a method of controlling an operation of a small Base Station (BS) and the small BS in a communication system.
2. Description of the Related Art
As terminals such as smart phones have gained popularity, the average amount of data that mobile communication users use is increasing exponentially. In addition, users' demands for higher data rates are also increasing gradually.
In general, a data rate is increased by conducting communication in a wider frequency band or by increasing spectral efficiency. However, there are limitations in increasing an average data rate by increasing spectral efficiency because preset communication technologies have already reached almost a theoretical limit of spectral efficiency and therefore it is difficult to increase the spectral efficiency above the theoretical limit by technology development. Accordingly, a method of providing a data service in a wider frequency band may be considered as a promising method for increasing data rate. Herein, an available frequency band should be considered. According to the present frequency distribution policy, a frequency band of 1 GHz or above is limited for broadband communication and an available frequency band is only a millimeter wave band of 30 GHz or above in practice. Compared to the 2-GHz band of general cellular systems (hereinafter, referred to as a ‘cellular frequency band’), a signal is attenuated significantly with respect to a distance in the extremely high frequency band. If a BS uses the same power as in a general cellular system, the BS's coverage is extremely reduced due to the signal attenuation. To avert this problem, beamforming is employed to increase the transmission and reception efficiency of antennas by focusing transmission and reception power toward a narrow space.
Because of high linearity and low transmittance unlike waves in a low frequency band, millimeter waves have a very low transmission and reception performance relative to the general cellular frequency band, particularly if an obstacle exists in a communication path between a BS and a Mobile Station (MS) or an MS is located within a closed room. To overcome this problem, small BSs may be installed, which operate within the service areas of macro BSs. A small BS refers to a BS having less transmission power and a smaller service area than a macro BS. Small BSs may include a femto BS, a pico BS, an indoor BS, a relay designed to expand cell coverage, and a Remote Radio Head (RRH). A macro BS and small BSs installed within the macro BS may interfere with one another in a specific situation such as when it is raining or snowing, or before the macro BS discontinues signal transmission. Accordingly, there exists a need for a method of efficiently using small BSs installed within the service area of a macro BS only in a specific situation.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present invention.